This invention related to the field of sawing, and more particularly to a device for orienting logs so as to maximize useful yield when the logs are sawn.
In a sawmill, as logs are moved longitudinally relative to a saw blade, either by moving the logs or by moving the saw, a cut substantially parallel to the log axis results. In order to maximize yield, the angularity of the log axis with respect to the direction of log movement may be controlled; the orientation of the log about its axis, with respect to the plane of the saw blade may also be controlled. These orientations become more important the more a particular log deviates from an ideal cylindrical shape.
A common variation from cylindrical shape in logs is "sweep", which term describes a log whose axis is curved, rather than being a straight line. Feeding mechanisms normally are not adapted to follow the sweep of the log, so straight-line sawing must be done in a way that maximizes yield from such a log. Although it is possible for a log axis to follow a corkscrew path, or other compound curve, it is more common for a log axis to follow a simple curve lying substantially in a single plane. For such a log, it can be shown that yields are maximized by cutting the log in planes parallel to the plane containing the log axis. Thus, where a saw blade lies in a vertical plane, the plane in which the log axis lies should also be vertical.
Prior devices have been proposed for controlling the orientation of logs as they are fed to a saw. U.S. Pat. Nos. 4,294,149, 4,365,704, 4,570,687 and 4,458,567 are representative. Optical scanners and the like may be used in association with log turners to properly orient logs for sawing, as in U.S. Pat. No. 4,294,149, above. Otherwise, the logs may be rotated manually, or by manually controlled machines, with the exercise of human judgment.